The invention relates to a data communication apparatus of the kind comprising a master unit and at least one physically separate, passive slave unit. The invention is concerned particularly, but not exclusively, with toys and games.
A number of electronic toys and games exist in which information cards or pieces are placed on a base, which base reads information off the pieces and provides an output such as verbal messages. A difficulty is that the base only contains a preprogrammed memory and can only perform the tasks it is made to do.
U.S. Pat. No. 5,190,285 describes an electronic game having a base and separate playing pieces or characters, each character containing a store for storing data which can be transferred to a processor attached to the base. The character is supplied with power via coils in the character and base respectively and communicates the data through a coupled capacitor plate. This is a relatively complex construction and in practice the use of capacitive coupling will result in very weak signals being transferred which is undesirable.
In accordance with the present invention, data communication apparatus comprises a master unit and at least one physically separate, passive slave unit, the master unit having a first part of an inductive communication system, and a processor connected to the first part of the inductive communication system, and the slave unit having a second part of the inductive communication system, a data store, and a modulator responsive to data from the data store and connected to the second part of the inductive communication system, wherein the first and second parts of the inductive communication system are constructed so that when the slave unit is brought into proximity with the master unit, power is inductively coupled from the master unit to the slave unit via the inductive communication system, and the modulator in the slave unit is thereby activated to cause data from the store to be inductively communicated from the slave unit to the master unit via the inductive communication system, the processor being responsive to the data supplied to the master unit.
With this invention, the inductive communication system is utilized both for supplying power to the slave unit and for receiving data from the slave unit. This results in a simpler construction, particularly for the slave unit.
In principle, any RF inductive communication system could be used but in the preferred arrangement, the inductive communication system comprises a tuned circuit. The use of a tuned circuit maximises power transfer and the phase change detected as well as increasing the selectivity of the apparatus so that a slave unit will only pass data to the master unit when they are in close proximity.
In this case, the modulator is preferably adapted to adjust the resonant frequency of the tuned circuit in accordance with data supplied from the data store. Effectively, the inductive arrangement defined by the tuned circuit is either tuned or detuned in accordance with the data. Detuning the system adjusts the tuned circuit""s resonant frequency which can be detected as a phase shift in the received signal relative to the drive signal fed to the tuned circuit by the processor.
In the preferred arrangement the processor generates a drive signal, at a drive frequency, which is fed to the first part of the tuned circuit, the tuned circuit being adapted to resonate at a frequency offset from the drive frequency when no data is being transmitted to the master unit, such that the tuned circuit oscillates at a frequency which is phase shifted relative to the drive frequency. The advantage of this offset is that in the case of binary data, whichever value the binary data has, there will be a phase shift in the received signal.
Typically, the frequency offset will be small, no more than 5%, preferably no more than 3.5%, of the resonant frequency of the drive frequency.
Typically, the modulator is responsive to binary data from the data store either to adjust or not to adjust the resonant frequency of the tuned circuit in accordance with the value of the data.
Conveniently, where the resonant frequency of the tuned circuit is offset from the drive frequency, the non-adjusted and adjusted resonant frequencies of the tuned circuit are on either side of the drive frequency. This provides a symmetrical arrangement which enhances detection.
It will be understood that the use of a phase change yields good noise immunity, comparable to FM modulation, in contrast to known amplitude modulation techniques.
In principle, the data stored in the data store could be fed directly to the modulator but in some cases this could introduce difficulties where successive digits have the same value leading to a DC level. To overcome this, preferably, the slave unit comprises a unit for converting each binary digit from the store into a two bit sequence in which the values of the bits are different, the order within the sequence varying depending upon the value of the binary digit from the data store. The converting unit could comprise, for example, an exclusive-OR gate.
This approach ensures that every binary digit received from the data store causes a variation in the manner in which the tuned circuit is modulated. For example, a binary value 1 from the data store could be converted to a sequence xe2x80x9c10xe2x80x9d while a binary value xe2x80x9c0xe2x80x9d could be converted to xe2x80x9c01xe2x80x9d.
Typically, the modulator comprises a switch for including one or more reactive elements into the tuned circuit, such as an additional capacitor. Conveniently, the modulator comprises a field effect transistor.
As previously mentioned, the master unit conveniently further comprises a phase comparator which receives a signal at the drive frequency, and the signal returned from the tuned circuit and generates an output signal related to the phase difference between the two input signals.
Typically, the master unit will also further comprise a converter unit connected to the output of the phase comparator for generating a pulse width modulated signal related to the phase difference defined by the signal output by the phase comparator. The converter unit could comprise an exclusive-OR gate as is known in the art.
The data stored in the data store can define a variety of types of information. For example, the data could define a programme to which the processor in the master unit responds. Typically, however, the master unit includes at least one output device adapted to generate one or more of an electrical, visual, audible and mechanical output under control of the processor, in response to data received from the slave unit.
It will be appreciated that the invention is particularly suited for use as a toy or game, the or each slave unit being incorporated in a toy character, model or card. The advantage of this is that a common master unit can be provided for use with a variety of toys or models each of which stores data related to the particular toy or model. For example, if the slave unit is incorporated in a toy character, the data stored in the data store may define an audio message intended to be the character speaking.
The invention has advantages for a toy manufacturer. One main advantage is that a user can acquire in the first instance a base containing the master unit and one set of pieces, each containing a respective slave unit, which together form one toy. But once a user is in possession of a base, a new toy can later be made by supplying a new set of pieces with different information in their respective data stores. Thus for example a first toy might consist of a base and a plurality of pieces in the form of well known cartoon characters which convey verbally to the user their name. The manufacturer could then supply different pieces such as models of different aeroplanes which could be provided in their respective data stores with a brief verbal description about their history. It is also envisaged that the information in the data store might form a programme to programme the processor, in the master unit. A toy might thus include one piece which programmes the processor to form the basis of the actions of the toy, and other pieces (which have less information in their respective data stores) could then be read by the processor once programmed. The processor could then become more sophisticated and cause mechanical actions to take place in addition to or as an alternative to audible and visual outputs.
In further arrangements, the processor could be linked to a further computer to form more complex toys. It should also be noted that although the invention has particular application to toys and games, it could also form part of an educational aid.
In other applications, the Tag could be used to provide information about an object, such as a file, to which it is attached. For security applications, the Tag could store a sample of the bearer""s voice for comparison with the bearer and/or information only known to the bearer. Many other audio/musical applications are possible.
In general the data store will be a ROM but in some cases a reprogrammable store could be used.